ppc4xx: Move gpio.h to ppc4xx-gpio.h since its ppc4xx specific

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/board/zeus/zeus.c b/board/zeus/zeus.c
index 4e6878a..a29e518 100644
--- a/board/zeus/zeus.c
+++ b/board/zeus/zeus.c
@@ -30,7 +30,7 @@
 
 #include <asm/processor.h>
 #include <asm/io.h>
-#include <asm/gpio.h>
+#include <asm/ppc4xx-gpio.h>
 
 DECLARE_GLOBAL_DATA_PTR;